/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.iotdb.library.dprofile;

import org.apache.commons.math3.distribution.ChiSquaredDistribution;
import org.apache.iotdb.library.util.Util;
import org.apache.iotdb.udf.api.UDTF;
import org.apache.iotdb.udf.api.access.Row;
import org.apache.iotdb.udf.api.collector.PointCollector;
import org.apache.iotdb.udf.api.customizer.config.UDTFConfigurations;
import org.apache.iotdb.udf.api.customizer.parameter.UDFParameterValidator;
import org.apache.iotdb.udf.api.customizer.parameter.UDFParameters;
import org.apache.iotdb.udf.api.customizer.strategy.RowByRowAccessStrategy;
import org.apache.iotdb.udf.api.type.Type;
import org.eclipse.collections.impl.list.mutable.primitive.DoubleArrayList;

/**
 * This function calculates acf, and then calculates p-value of corresponding Q_LB statistics.
 */
public class UDTFQLB implements UDTF {

    private final DoubleArrayList valueArrayList = new DoubleArrayList();
    private int m = 0;
    private double qlb = 0.0f;

    @Override
    public void validate(UDFParameterValidator validator) throws Exception {
        validator
                .validateInputSeriesNumber(1)
                .validateInputSeriesDataType(0, Type.INT32, Type.INT64, Type.FLOAT, Type.DOUBLE)
                .validate(
                        x -> (int) x >= 0,
                        "Parameter $lag$ should be an positive integer, or '0' for default value.",
                        validator.getParameters().getIntOrDefault("lag", 0));
    }

    @Override
    public void beforeStart(UDFParameters parameters, UDTFConfigurations configurations)
            throws Exception {
        configurations.setAccessStrategy(new RowByRowAccessStrategy()).setOutputDataType(Type.DOUBLE);
        m = parameters.getIntOrDefault("lag", 0);
        valueArrayList.clear();
    }

    @Override
    public void transform(Row row, PointCollector collector) throws Exception {
        if (row.isNull(0)) {
            valueArrayList.add(Double.NaN);
        } else {
            double v = Util.getValueAsDouble(row);
            if (Double.isFinite(v)) {
                valueArrayList.add(v);
            } else {
                valueArrayList.add(0d);
            }
        }
    }

    @Override
    public void terminate(PointCollector collector) throws Exception {
        int n = valueArrayList.size();
        if (m <= 0 || m >= n) {
            m = n - 2;
        }
        for (int shift = 1; shift <= m; shift++) {
            double correlation = 0.0;
            for (int i = 0; i < n - shift; i++) {
                if (Double.isFinite(valueArrayList.get(shift + i))
                        && Double.isFinite(valueArrayList.get(i))) {
                    correlation += valueArrayList.get(shift + i) * valueArrayList.get(i);
                }
            }
            correlation = correlation / n;
            collector.putDouble((long) n + shift, correlation);
            qlb += correlation * correlation / (n - shift) * n * (n + 2);
            ChiSquaredDistribution qlbdist = new ChiSquaredDistribution(shift);
            double qlbprob = 1.0 - qlbdist.cumulativeProbability(qlb);
            collector.putDouble(shift, qlbprob);
        }
    }

    @Override
    public void beforeDestroy() {
        valueArrayList.clear();
    }
}
